Yesterday I ran Disk Utility to repair my external USB drive, which I use for Time Machine and SuperDuper backups. (there were lots of issues found...) Note: this was a disk repair, not a permissions repair.

Today my first SuperDuper smart backup (since yesterday's repair) failed. Here are the last two lines of the log:

Well, I have no idea what went wrong, so I can't suggest replacing the drive. But starting over (erasing the drive) seems sensible, as long as you don't need the history (and, since these things are pruned, and it's not an 'archive', that's often a reasonable thing to do).

I'm normally very careful with the external drive, especially while its running, but during the last backup it got pulled to the (carpeted) floor from the couch, an 18" drop, DURING a backup... not good, I know...

I guess I'll reformat it and run a repair frequently, watching for errors.